Generally, in a reciprocating compressor, a compression space to/from which an operation gas is sucked and discharged is defined between a piston and cylinder, so that the piston is linearly reciprocated inside the cylinder to compress refrigerant.
Since the reciprocating compressor includes a component for converting a rotation force of a driving motor into a linear reciprocation force of the piston, such as a crank shaft, a large mechanical loss occurs due to the motion conversion. Recently, a linear compressor has been actively developed to solve the foregoing problem.
In the linear compressor, particularly, a piston is connected directly to a linearly-reciprocated linear motor to prevent the mechanical loss by the motion conversion, improve the compression efficiency and simplify the configuration. Power inputted to the linear motor can be regulated to control the operation thereof. Accordingly, since the linear compressor can reduce noise more than the other compressors, it has been mostly applied to electric home appliances used indoors, such as a refrigerator.
FIG. 1 is a view illustrating an example of a conventional linear compressor.
In the conventional linear compressor, a structure composed of a frame 1, a cylinder 2, a piston 3, a suction valve 4, a discharge valve assembly 5, a linear motor 6, a motor cover 7, a supporter 8, a rear cover 9, main springs S1 and S2 and a muffler assembly 10 is installed to be elastically supported inside a shell (not shown).
The cylinder 2 is fixedly fitted into the frame 1, the discharge valve assembly 5 composed of a discharge valve 5a, a discharge cap 5b and a discharge valve spring 5c is installed to block one end of the cylinder 2, the piston 3 is inserted into the cylinder 2, and the thin suction valve 4 is installed to open and close an outlet 3a of the piston 2.
In the linear motor 6, a permanent magnet 6c is installed to be linearly reciprocated, maintaining an air-gap between an inner stator 6a and an outer stator 6b. The permanent magnet 6c is connected to the piston 3 by a connection member 6d, and linearly reciprocated due to a mutual electromagnetic force between the inner stator 6a, the outer stator 6b and the permanent magnet 6c to thereby operate the piston 3.
The motor cover 7 supports the outer stator 6b in an axis direction to fix the outer stator 6b, and is bolt-fixed to the frame 1. The rear cover 9 is coupled to the motor cover 7. The supporter 8 connected to the other end of the piston 3 is installed between the motor cover 7 and the rear cover 9 to be elastically supported by the main springs S1 and S2 in an axis direction. The muffler assembly 10 for sucking refrigerant is fastened together with the supporter 8. The reference number 20 indicates a mass member installed on the supporter 8.
Here, the main springs S1 and S2 include four front springs S1 and four rear springs S2 in up-down and left-right positions symmetric around the supporter 8. When the linear motor 6 is operated, the front springs S1 and the rear springs S2 are driven in the opposite directions to buff the piston 3 and the supporter 8. Besides, refrigerant in a compression space P serves as a kind of gas spring to buff the piston 3 and the supporter 8.
Therefore, when the linear motor 6 is operated, the piston 3 and the muffler assembly 10 connected thereto are linearly reciprocated. Since a pressure inside the compression space P is varied, the operations of the suction valve 4 and the discharge valve assembly 5 are automatically controlled. During the operation, refrigerant flows through a suction tube on the shell side, an opening portion of the rear cover 9, the muffler assembly 10 and an inlet 3a of the piston 3, is sucked into and compressed in the compression space P, and is externally discharged through the discharge cap 5b, a loop pipe and a discharge tube on the shell side.
FIG. 2 is a view illustrating an example of an installation structure of the motor cover and the rear cover of the conventional linear compressor. The conventional motor cover 7 is formed in the shape of a disk with a central opening portion so that the piston 3 (refer to FIG. 1) can pass through the opening portion. A pair of spring supporting portions protruding to support the front main springs S1 (refer to FIG. 1) with the supporter 8 (refer to FIG. 1) are provided at both sides of the opening portion, respectively. A protruding end 8 protruding in an axis direction opposite to the compression space P (refer to FIG. 1) is provided at a rim portion of the motor cover 7. A plurality of bolt holes 9c are formed in portions coupled to the rear cover 9 inside the protruding end.
The conventional rear cover 9 is formed in the shape of a plate with a central opening portion so that a part of the muffler assembly 10 (refer to FIG. 1) can be mounted on the opening portion. A pair of spring supporting portions 9a protruding to support the rear main spring S2 (refer to FIG. 1) are provided at both sides of the opening portion, respectively. A pair of supporting ends 9b bent toward the compression space P (refer to FIG. 1) and then outwardly bent to be brought into contact with the motor cover 7 are provided at both ends of the rear cover 9. A plurality of bolt holes 9c are formed in portions of the supporting ends 9b coupled to the motor cover 7.
When the motor cover 7 and the supporting ends 9b of the rear cover 9 are brought into contact, bolts B are fastened to the bolt holes 9c of the motor cover 7 and the bolt holes 9c of the rear cover 9. Here, a plurality of spacers 7d can be installed in the contact portions of the motor cover 7 and the supporting ends 9b of the rear cover 9 to maintain a predetermined interval in an axis direction. A dimension design value is different in each product model, and a dimension tolerance is generated during an assembly process. In this circumstance, so as to compensate for a dimension variation value, the spacers 7d are used to regulate a distance from the motor cover 7 to the rear cover 9.
However, in the conventional reciprocating compressor, in order to adjust an initial design value, an assembly tolerance and a measurement tolerance, the spacers are inserted between the motor cover and the rear cover of fixed standard, and the motor cover, the spacers and the rear cover are bolt-assembled at a time. As a result, the assembly time increases and the production cost rises because of the spacers.